A halohydantoin compound has been widely used as a sensitizer for a photograph or the like or as a halogenating agent or an oxidizing agent for use in a process of producing a medicinal product, an agricultural chemical, a compound, or the like. In particular, 1,3-diiodo-5,5-dimethylhydantoin, which is a halohydantoin compound, is considered as a promising compound, as 1,3-diiodo-5,5-dimethylhydantoin is high in iodine content and a more economical method for producing 1,3-diiodo-5,5-dimethylhydantoin has been disclosed. As a method for producing 1,3-diiodo-5,5-dimethylhydantoin, for example, a method including the step of causing 5,5-dimethylhydantoin and iodine monochloride to react with each other in the presence of a base in a mixed solvent of an aqueous solution and an organic solvent and a refining method have been disclosed (see, for example, Patent Literature 1 and Non Patent Literature 1).
Non Patent Literature 1 describes the following method: 5,5-dimethylhydantoin and iodine monochloride are reacted with each other with use of a sodium hydroxide aqueous solution and carbon tetrachloride. The resulting crystals are washed with water, and are further washed with anhydrous ethyl acetate. After that, the crystals are dried at 60° C. under reduced pressure. Thereby, 1,3-diiodo-5,5-dimethylhydantoin is refined. Non Patent Literature 1 further states that the resulting 1,3-diiodo-5,5-dimethylhydantoin is a reagent so stable that it can be preserved in a desiccator in a dark place without recrystallizing.
Further, Patent Literature 1 gives the following description: First, 5,5-dimethylhydantoin and iodine monochloride are reacted with each other in a sodium hydroxide aqueous solution with use of N,N-dimethylformamide or an n-butyl acetate solvent. Next, the precipitated crystals as a result of the reaction are collected by filtration, and then, dried under reduced pressure, thereby being refined.